Techniques for optical source pitch reduction

ABSTRACT

A light detection and ranging (LIDAR) system includes a first optical source to generate a first optical beam, a first collimating lens to collimate the first optical beam, a first prism wedge of a first prism wedge pair to redirect the first optical beam, and a first focusing lens to focus the first optical beam on a front surface of a second prism wedge of the first prism wedge pair, the second prism wedge to direct the first optical beam toward an output lens.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.17/093,599, filed Nov. 9, 2020, the entire contents of which are herebyincorporated by reference.

FIELD OF INVENTION

The present disclosure is related to light detection and ranging (LIDAR)systems in general, and more particularly to image conjugate pitchreduction of a LIDAR system.

BACKGROUND

Frequency-Modulated Continuous-Wave (FMCW) LIDAR systems use tunablelasers for frequency-chirped illumination of targets, and coherentreceivers for detection of backscattered or reflected light from thetargets that are combined with a local copy of the transmitted signal(LO signal). Conventional LIDAR systems require high frame rates and anincreased number of scanning points typically achieved by using multiplenumbers of optical sources to emit optical beams. The optical sourcesmay be placed in a one-dimensional or two-dimensional array separated bysome distance, referred to as pitch. The array of optical sources mayshare a single output lens. The single output lens provides angularseparation between collimated optical beams to create discrete linesafter reaching the scanner of the LIDAR system. Using the single outputlens for multiple optical beams may reduce the cost form factor of thesystem in comparison to adding additional output lenses. However, asmore optical beams are added to the system using a single output lens,the decenter of the beams on the output lens is increased, resulting inchanges in numerical aperture (NA) of the system as well as an increasein aberration content of the output beams.

SUMMARY

The present disclosure describes various examples of LIDAR systems andmethods for optical source pitch reduction.

In some embodiments, a light detection and ranging (LIDAR) systemincludes a first optical source to generate a first optical beam, afirst collimating lens to collimate the first optical beam, a firstprism wedge of a first prism wedge pair to redirect the first opticalbeam, and a first focusing lens to focus the first optical beam on afront surface of a second prism wedge of the first prism wedge pair, thesecond prism wedge to direct the first optical beam toward an outputlens.

In some embodiments, the LIDAR system includes a second optical sourceto generate a second optical beam, a second collimating lens tocollimate the second optical beam, a third prism wedge of a second prismwedge pair to redirect the second optical beam, and a second focusinglens to focus the second optical beam on a front surface of a fourthprism wedge of the second prism wedge pair, the fourth prism wedge todirect the second optical beam toward the output lens.

In some embodiments, a spacing of the first and second optical beams atthe output lens is determined by an angle of the first prism wedge pairand the second prism wedge pair and a first focal length of the firstfocusing lens and a second focal length of the second focusing lens. Insome embodiments, the first collimating lens is spaced a first distancefrom the first optical source, the first distance corresponding to afocal length of the first collimating lens. In some embodiments, thesecond prism wedge is spaced a second distance from the first focusinglens, the second distance corresponding to a focal length of the firstfocusing lens. In some embodiments, the output lens creates an angularseparation between the first optical beam and the second optical beam.

In some embodiments, the angular separation between the first opticalbeam and the second optical beam is less than two degrees. In someembodiments, the angular separation between the first and second opticalbeams is determined by a spacing between the first and second opticalbeams and a focal length of the output lens. In some embodiments, thefirst prism wedge pair is adjustable to calibrate a first decenter forthe first optical beam with respect to the output lens. In someembodiments, the output lens transmits the first optical beam to scanneroptics of the LIDAR system.

In some embodiments, a method includes generating a first optical beamat a first optical source, collimating the first optical beam using afirst collimating lens, and redirecting the first optical beam using afirst prism wedge of a first prism wedge pair. The method furtherincludes focusing the first optical beam on a second prism wedge of thefirst prism wedge pair using a first focusing lens and redirecting thefirst optical beam toward an output lens using the second prism wedge.

In some embodiments, the method further includes generating a secondoptical beam at a second optical source, collimating the second opticalbeam using a second collimating lens, redirecting the second opticalbeam using a third prism wedge of a second prism wedge pair, focusingthe second optical beam on a fourth prism wedge of the second prismwedge pair using a second focusing lens, and redirecting the secondoptical beam toward the output lens using the fourth prism wedge.

In some embodiments, a spacing of the first and second optical beams isdetermined by an angle of the first prism wedge pair and the secondprism wedge pair and a first focal length of the first focusing lens andsecond focal length of the second focusing lens. In some embodiments,the first collimating lens is spaced a first distance from the firstoptical source, the first distance corresponding to a focal length ofthe first collimating lens. In some embodiments, the second prism wedgeis spaced a second distance from the first focusing lens, the seconddistance corresponding to a focal length of the first focusing lens.

In some embodiments, the method further includes creating an angularseparation of the first optical beam and second optical beam using theoutput lens. In some embodiments, the angular separation is based on aspacing between the first optical beam and the second optical beam atthe output lens. In some embodiments, the angular separation between thefirst optical beam and the second optical beam is less than two degrees.In some embodiments, the method further includes adjusting the firstprism wedge pair to calibrate a first decenter for the first opticalbeam with respect to the output lens. In some embodiments, the outputlens transmits the first optical beam to scanner optics.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the various examples, reference isnow made to the following detailed description taken in connection withthe accompanying drawings in which like identifiers correspond to likeelements.

FIG. 1 illustrates an example FMCW LIDAR system according to embodimentsof the present disclosure.

FIG. 2 is a time-frequency diagram illustrating an example of FMCW LIDARwaveforms according to embodiments of the present disclosure.

FIG. 3 is a block diagram of an example LIDAR system according toembodiments of the present disclosure.

FIG. 4 is a block diagram of an example optical system according toembodiments of the present disclosure.

FIG. 5A is an illustration of optical beam spacing at an optical sourcearray according to embodiments of the present disclosure.

FIG. 5B is an illustration of optical beam spacing at an image conjugateposition according to embodiments of the present disclosure.

FIG. 5C is an illustration of an output optical beam separationaccording to embodiments of the present disclosure.

FIG. 6 is a flow diagram of an example method for reducing imageconjugate pitch according to embodiments of the present disclosure.

FIG. 7 is a block diagram of another example optical system to reduceimage conjugate pitch according to embodiments of the presentdisclosure.

DETAILED DESCRIPTION

The present disclosure describes various examples of LIDAR systems andmethods for image conjugate pitch reduction. According to someembodiments, the described LIDAR system may be implemented in anysensing market, such as, but not limited to, transportation,manufacturing, metrology, medical, and security systems. According tosome embodiments, the described LIDAR system is implemented as part of afront-end of frequency modulated continuous-wave (FMCW) device thatassists with spatial awareness for automated driver assist systems, orself-driving vehicles.

The present disclosure addresses the above issues associated with addingadditional optical beams to a single output lens of a LIDAR system byreducing the pitch (i.e., spacing) between the optical beams prior toreaching the output lens. In one example, the present disclosure reducesthe pitch using a dual prism architecture with a collimating lens and afocusing lens for each of the optical beams. The collimating lens mayfirst collimate an optical beam into a first prism wedge. The prism mayangle the optical beam towards the focusing lens (i.e., toward a centeraxis of the output lens) which may focus the optical beam on a frontsurface of a second prism wedge. The second prism wedge may redirect theoptical beam toward the output lens at a reduced decenter resulting inreduced spacing between optical beams. The reduced spacing betweenoptical beams may reduce aberrations in the output beams and may alsoprovide for reduced angular separation between the output optical beams.

FIG. 1 illustrates a LIDAR system 100 according to exampleimplementations of the present disclosure. The LIDAR system 100 includesone or more of each of a number of components, but may include fewer oradditional components than shown in FIG. 1. As shown, the LIDAR system100 includes optical circuits 101 implemented on a photonics chip. Theoptical circuits 101 may include a combination of active opticalcomponents and passive optical components. Active optical components maygenerate, amplify, and/or detect optical signals and the like. In someexamples, the active optical component includes optical beams atdifferent wavelengths, and includes one or more optical amplifiers, oneor more optical detectors, or the like.

Free space optics 115 may include one or more optical waveguides tocarry optical signals, and route and manipulate optical signals toappropriate input/output ports of the active optical circuit. The freespace optics 115 may also include one or more optical components such astaps, wavelength division multiplexers (WDM), splitters/combiners,polarization beam splitters (PBS), collimators, couplers or the like. Insome examples, the free space optics 115 may include components totransform the polarization state and direct received polarized light tooptical detectors using a PBS, for example. The free space optics 115may further include a diffractive element to deflect optical beamshaving different frequencies at different angles along an axis (e.g., afast-axis).

In some examples, the LIDAR system 100 includes an optical scanner 102that includes one or more scanning mirrors that are rotatable along anaxis (e.g., a slow-axis) that is orthogonal or substantially orthogonalto the fast-axis of the diffractive element to steer optical signals toscan an environment according to a scanning pattern. For instance, thescanning mirrors may be rotatable by one or more galvanometers. Objectsin the target environment may scatter an incident light into a returnoptical beam or a target return signal. The optical scanner 102 alsocollects the return optical beam or the target return signal, which maybe returned to the passive optical circuit component of the opticalcircuits 101. For example, the return optical beam may be directed to anoptical detector by a polarization beam splitter. In addition to themirrors and galvanometers, the optical scanner 102 may includecomponents such as a quarter-wave plate, lens, anti-reflective coatedwindow or the like.

To control and support the optical circuits 101 and optical scanner 102,the LIDAR system 100 includes LIDAR control systems 110. The LIDARcontrol systems 110 may include a processing device for the LIDAR system100. In some examples, the processing device may be one or moregeneral-purpose processing devices such as a microprocessor, centralprocessing unit, or the like. More particularly, the processing devicemay be complex instruction set computing (CISC) microprocessor, reducedinstruction set computer (RISC) microprocessor, very long instructionword (VLIW) microprocessor, or processor implementing other instructionsets, or processors implementing a combination of instruction sets. Theprocessing device may also be one or more special-purpose processingdevices such as an application specific integrated circuit (ASIC), afield programmable gate array (FPGA), a digital signal processor (DSP),network processor, or the like.

In some examples, the LIDAR control systems 110 may include a signalprocessing unit 112 such as a DSP. The LIDAR control systems 110 areconfigured to output digital control signals to control optical drivers103. In some examples, the digital control signals may be converted toanalog signals through signal conversion unit 106. For example, thesignal conversion unit 106 may include a digital-to-analog converter.The optical drivers 103 may then provide drive signals to active opticalcomponents of optical circuits 101 to drive optical sources such aslasers and amplifiers. In some examples, several optical drivers 103 andsignal conversion units 106 may be provided to drive multiple opticalsources.

The LIDAR control systems 110 are also configured to output digitalcontrol signals for the optical scanner 102. A motion control system 105may control the galvanometers of the optical scanner 102 based oncontrol signals received from the LIDAR control systems 110. Forexample, a digital-to-analog converter may convert coordinate routinginformation from the LIDAR control systems 110 to signals interpretableby the galvanometers in the optical scanner 102. In some examples, amotion control system 105 may also return information to the LIDARcontrol systems 110 about the position or operation of components of theoptical scanner 102. For example, an analog-to-digital converter may inturn convert information about the galvanometers' position to a signalinterpretable by the LIDAR control systems 110.

The LIDAR control systems 110 are further configured to analyze incomingdigital signals. In this regard, the LIDAR system 100 includes opticalreceivers 104 to measure one or more beams received by optical circuits101. For example, a reference beam receiver may measure the amplitude ofa reference beam from the active optical component, and ananalog-to-digital converter converts signals from the reference receiverto signals interpretable by the LIDAR control systems 110. Targetreceivers measure the optical signal that carries information about therange and velocity of a target in the form of a beat frequency,modulated optical signal. The reflected beam may be mixed with a secondsignal from a local oscillator. The optical receivers 104 may include ahigh-speed analog-to-digital converter to convert signals from thetarget receiver to signals interpretable by the LIDAR control systems110. In some examples, the signals from the optical receivers 104 may besubject to signal conditioning by signal conditioning unit 107 prior toreceipt by the LIDAR control systems 110. For example, the signals fromthe optical receivers 104 may be provided to an operational amplifierfor amplification of the received signals and the amplified signals maybe provided to the LIDAR control systems 110.

In some applications, the LIDAR system 100 may additionally include oneor more imaging devices 108 configured to capture images of theenvironment, a global positioning system 109 configured to provide ageographic location of the system, or other sensor inputs. The LIDARsystem 100 may also include an image processing system 114. The imageprocessing system 114 can be configured to receive the images andgeographic location, and send the images and location or informationrelated thereto to the LIDAR control systems 110 or other systemsconnected to the LIDAR system 100.

In operation according to some examples, the LIDAR system 100 isconfigured to use nondegenerate optical sources to simultaneouslymeasure range and velocity across two dimensions. This capability allowsfor real-time, long range measurements of range, velocity, azimuth, andelevation of the surrounding environment.

In some examples, the scanning process begins with the optical drivers103 and LIDAR control systems 110. The LIDAR control systems 110instruct the optical drivers 103 to independently modulate one or moreoptical beams, and these modulated signals propagate through the passiveoptical circuit to the collimator. The collimator directs the light atthe optical scanning system that scans the environment over apreprogrammed pattern defined by the motion control system 105. Theoptical circuits 101 may also include a polarization wave plate (PWP) totransform the polarization of the light as it leaves the opticalcircuits 101. In some examples, the polarization wave plate may be aquarter-wave plate or a half-wave plate. A portion of the polarizedlight may also be reflected back to the optical circuits 101. Forexample, lensing or collimating systems used in LIDAR system 100 mayhave natural reflective properties or a reflective coating to reflect aportion of the light back to the optical circuits 101.

Optical signals reflected back from the environment pass through theoptical circuits 101 to the receivers. Because the polarization of thelight has been transformed, it may be reflected by a polarization beamsplitter along with the portion of polarized light that was reflectedback to the optical circuits 101. Accordingly, rather than returning tothe same fiber or waveguide as an optical source, the reflected light isreflected to separate optical receivers. These signals interfere withone another and generate a combined signal. Each beam signal thatreturns from the target produces a time-shifted waveform. The temporalphase difference between the two waveforms generates a beat frequencymeasured on the optical receivers (photodetectors). The combined signalcan then be reflected to the optical receivers 104.

The analog signals from the optical receivers 104 are converted todigital signals using ADCs. The digital signals are then sent to theLIDAR control systems 110. A signal processing unit 112 may then receivethe digital signals for further processing. In some embodiments, thesignal processing unit 112 also receives position data from the motioncontrol system 105 and galvanometers (not shown) as well as image datafrom the image processing system 114. The signal processing unit 112 canthen generate 3D point cloud data with information about range andvelocity of points in the environment as the optical scanner 102 scansadditional points. The signal processing unit 112 can also overlay 3Dpoint cloud data with the image data to determine velocity and distanceof objects in the surrounding area. The system also processes thesatellite-based navigation location data to provide a precise globallocation.

FIG. 2 is a time-frequency diagram 200 of an FMCW scanning signal 201that can be used by a LIDAR system, such as system 100, to scan a targetenvironment according to some embodiments. In one example, the scanningwaveform 201, labeled as f_(FM)(t), is a sawtooth waveform (sawtooth“chirp”) with a chirp bandwidth Δf_(C) and a chirp period T_(C). Theslope of the sawtooth is given as k=(Δf_(C)/T_(C)). FIG. 2 also depictstarget return signal 202 according to some embodiments. Target returnsignal 202, labeled as f_(FM)(t-Δt), is a time-delayed version of thescanning signal 201, where Δt is the round trip time to and from atarget illuminated by scanning signal 201. The round trip time is givenas Δt=2R/v, where R is the target range and v is the velocity of theoptical beam, which is the speed of light c. The target range, R, cantherefore be calculated as R=c(Δt/2). When the return signal 202 isoptically mixed with the scanning signal, a range dependent differencefrequency (“beat frequency”) Δf_(R)(t) is generated. The beat frequencyΔf_(R)(t) is linearly related to the time delay Δt by the slope of thesawtooth k. That is, Δf_(R)(t)=kΔt. Since the target range R isproportional to Δt, the target range R can be calculated asR=(c/2)(Δf_(R)(t)/k). That is, the range R is linearly related to thebeat frequency Δf_(R)(t). The beat frequency Δf_(R)(t) can be generated,for example, as an analog signal in optical receivers 104 of system 100.The beat frequency can then be digitized by an analog-to-digitalconverter (ADC), for example, in a signal conditioning unit such assignal conditioning unit 107 in LIDAR system 100. The digitized beatfrequency signal can then be digitally processed, for example, in asignal processing unit, such as signal processing unit 112 in system100. It should be noted that the target return signal 202 will, ingeneral, also includes a frequency offset (Doppler shift) if the targethas a velocity relative to the LIDAR system 100. The Doppler shift canbe determined separately, and used to correct the frequency of thereturn signal, so the Doppler shift is not shown in FIG. 2 forsimplicity and ease of explanation. It should also be noted that thesampling frequency of the ADC will determine the highest beat frequencythat can be processed by the system without aliasing. In general, thehighest frequency that can be processed is one-half of the samplingfrequency (i.e., the “Nyquist limit”). In one example, and withoutlimitation, if the sampling frequency of the ADC is 1 gigahertz, thenthe highest beat frequency that can be processed without aliasing(Δf_(Rmax)) is 500 megahertz. This limit in turn determines the maximumrange of the system as R_(max)=(c/2)(Δf_(Rmax)/k) which can be adjustedby changing the chirp slope k. In one example, while the data samplesfrom the ADC may be continuous, the subsequent digital processingdescribed below may be partitioned into “time segments” that can beassociated with some periodicity in the LIDAR system 100. In oneexample, and without limitation, a time segment might correspond to apredetermined number of chirp periods T, or a number of full rotationsin azimuth by the optical scanner.

FIG. 3 illustrates an example LIDAR system 300 to reduce a pitch (i.e.,spacing) of optical beams provided to a single output collimating lens.Optical system 300 includes an optical source array 310, pitch reductionoptics 320, and an output lens 330. The optical source array 310 mayinclude several optical sources that are separated by a certain spacing,referred to as pitch. Reducing the pitch between optical sources isdesirable in order to provide for more optical sources at the outputlens 330, to reduce aberrations due to large decenter at the output lens330 and to reduce an output angle 340 between the optical beams. In oneembodiment, the pitch between the optical beams may be reduced usingpitch reduction optics 320. Pitch reduction optics 320 may receiveoptical beams at a first pitch corresponding to the pitch of the opticalsources and reduce the pitch between the optical beams prior to reachingthe output lens 330. The reduced pitch may provide for smaller decenterof each of the optical beams at the output lens 330, resulting in asmaller output angle 340 between the optical beams without changing thefocal length of the output lens 330. The pitch reduction optics 320 mayinclude free space optics (e.g., free space optics 115 described in FIG.1), silicon optics, or any other type of optics to redirect the opticalbeams in a manner that reduces the pitch between the optical beams. Anexample embodiment of pitch reduction optics 320 is described in moredetail below with respect to FIG. 4. The LIDAR system 300 may alsoinclude scanner optics 350, such as one or more galvo mirrors to scan afield of view (FOV) of the LIDAR system 300.

The pitch of the optical beams received at the output lens 330 maydetermine the output angle 340 at which the optical beams will betransmitted from the LIDAR system 300. The output angle may also dependon the focal length of the output lens. For example, the output angleseparation between beams may be calculated from equation (1) below:

$\begin{matrix}{\theta = {{arc}\;{\tan( \frac{\frac{pitch}{n}}{FL} )}}} & (1)\end{matrix}$where θ is the output angle 340 between optical beams, pitch is thespacing between the optical beams, n is the number of optical beams, andFL is the focal length of the output lens 330. The reduced pitch betweenthe optical beams may provide for an output angle of less than twodegrees. In some embodiments, the reduced pitch may provide for anoutput angle of less than one degree.

FIG. 4 illustrates an example optical system 400 to reduce a pitch ofoptical beams provided to a single output collimating lens. Opticalsystem 400 includes an optical source array 401 to produce severaloptical beams. Although FIG. 4 depicts only two optical sourcesgenerating two corresponding optical beams, the optical source array 401may include any number of optical sources in either a one-dimensional ortwo-dimensional array. In one embodiment, optical source array 401 mayinclude three or more optical sources. LIDAR system 400 further includesoptics to redirect one or more optical beams and to reduce the decenterof each optical beam on an output lens 410. The optics to redirect eachoptical beam may include a collimating lens 402A-B, a first prism wedge404A-B, a focusing lens 406A-B, and a second prism wedge 408A-B.

In one embodiment, collimating lens 402A-B may receive an optical beamfrom the optical source array 401 and collimate the optical beam. Theoptical beam as collimated may be directed toward the first prism wedge404A-B. The second prism wedge 408A-B may redirect the optical beam inthe direction of the output lens center axis 412 (i.e., in a directionto reduce the decenter of the optical beam). The reduction in thedecenter of each optical beam may be dependent on the angle of the firstprism wedge 404A-B and the focal length of the focusing lens 406A-B. Inone embodiment, the angle of the first prism wedges 404A-B can beadjusted to calibrate the decenter of the optical beam and the pitchbetween the optical beams. A focusing lens 406A-B may receive theredirected optical beam from the first prism wedge 404A-B and focus theoptical beam at a front surface of a second prism wedge 408A-B. Thesecond prism wedges 408A-B may redirect the optical beam toward theoutput lens 410. The second prism wedges 408A-B may redirect the opticalbeam to be parallel with the output lens center axis 412 and each of theother optical beams. Therefore, as can be seen from FIG. 4, each opticalbeam from the optical source array 401 may be redirected to have areduced decenter on the output lens 410 than would be provided by thepitch of the optical sources of the optical source array 401.

In one embodiment, a local oscillator (LO) may be generated at the frontsurface of the second prism wedge 408A-B. For example, the front surfaceof the second prism wedge 408A-B may be partially reflective (e.g., apartially reflective coating, surface, etc.). Therefore, a portion ofthe optical beam may be reflected by the second prism wedge 408A-B as anLO of the optical beam.

FIG. 5A depicts a cross-sectional view of an exemplary optical beampitch at the optical source array 401 in accordance with FIG. 4. Theoptical beam pitch (i.e., spacing) at the optical source array 401 maybe limited by the structure of the optical sources and manufacturingconstraints of the optical beam array.

FIG. 5B depicts a cross-sectional view of an exemplary optical beampitch at the source conjugate position after pitch reduction. The sourceconjugate position as depicted may be directly after the second wedge408A-B, as depicted in FIG. 4. The dashed circles depicted in FIG. 5Amay illustrate the pitch at which the optical beams would be at withoutthe optical system (e.g., optical system 400) to reduce the optical beampitch. Therefore, as shown, the optical beam pitch at the sourceconjugate position may be reduced as compared to the optical beam pitchat the optical source array (e.g., optical source array 401).

FIG. 5C illustrates an example of the optical beam at an output of LIDARsystems described herein according to some embodiments. The optical beamseparation at the LIDAR output may be directly dependent on the pitchbetween the optical beams at the source conjugate position, andaccordingly the decenter of each beam incident on the output lens (e.g.,output lens 410 of FIG. 4).

FIG. 6 is a flowchart illustrating an example method 600 in a LIDARsystem for image conjugate pitch reduction.

With reference to FIG. 6, method 600 illustrates example functions usedby various embodiments. Although specific function blocks (“blocks”) aredisclosed in method 600, such blocks are examples. That is, embodimentsare well suited to performing various other blocks or variations of theblocks recited in method 600. It is appreciated that the blocks inmethod 600 may be performed in an order different than presented, andthat not all of the blocks in method 600 may be performed.

Method 600 begins at block 610, where a first optical source generates afirst optical beam and a second optical source generates a secondoptical beam. The first and second optical beams may be separated by afirst spacing. The first spacing may correspond to the spacing of thefirst and second optical sources. A chief ray of each of the first andsecond optical beams may be substantially parallel to one another.

At block 620, an optical system reduces the first spacing between thefirst and second optical beams to a second spacing. The optical systemmay include several sets of optics to redirect each optical beam. Forexample, the optical system may include a first set of optics to reducea decenter of a first optical beam and a second set of optics to reducea decenter of the second optical beam. Each set of optics may include atleast a prism wedge pair to change the direction of the optical beams.The sets of optics may also include a collimating lens to firstcollimate the optical beams toward a first prism wedge of a prism wedgepair. The first prism wedge may direct the optical beam to a focusinglens. The focusing lens may focus the optical beam at a front surface ofa second prism wedge. The second prism wedge may be complimentary to thefirst prism wedge to redirect the optical beam toward the output lens ona trajectory parallel to the original optical beam generated by theoptical source.

At block 630, the optical system transmits the first and second opticalbeams to an output lens. The output lens may provide an angularseparation between the first and second optical beams. The angularseparation may depend on the spacing between the first and secondoptical beams. The angular separation may provide for distinct lines toscan a scene in the FOV of the LIDAR system to avoid overlap ofcollected data points.

FIG. 7 illustrates another example embodiment of an optical system 700to reduce a pitch of optical beams provided to a single outputcollimating lens 702. Optical system 700 includes an optical sourcearray 701 including four optical sources and associated sets of opticsto reduce the pitch of the optical beams generated by the opticalsources. In one embodiment, each set of optics includes a wedge pair toreduce the decenter of each optical beam and the separation between thefour optical beams. The inner wedge pairs 710 and 715 may have wedgeangles to reduce the pitch of the inner optical beams by a particulardistance. The outer wedge pairs 705 and 720 may have larger wedge anglesto reduce the pitch of the outer optical beams by a larger distance thanthe inner wedges. The larger wedge angles of the outer wedge pairs 705and 720 may provide for similar spacing between each of the opticalbeams at the output lens. It should be noted that optical system 700 maybe extended to any number of optical sources as well as any combinationof optics to reduce the pitch of the optical sources in focal space. Asadditional optical sources are added in parallel, the wedge angles ofthe optics for the additional sources may be increased accordingly asthey are further from center.

The preceding description sets forth numerous specific details such asexamples of specific systems, components, methods, and so forth, inorder to provide a thorough understanding of several examples in thepresent disclosure. It will be apparent to one skilled in the art,however, that at least some examples of the present disclosure may bepracticed without these specific details. In other instances, well-knowncomponents or methods are not described in detail or are presented insimple block diagram form in order to avoid unnecessarily obscuring thepresent disclosure. Thus, the specific details set forth are merelyexemplary. Particular examples may vary from these exemplary details andstill be contemplated to be within the scope of the present disclosure.

Any reference throughout this specification to “one example” or “anexample” means that a particular feature, structure, or characteristicdescribed in connection with the examples are included in at least oneexample. Therefore, the appearances of the phrase “in one example” or“in an example” in various places throughout this specification are notnecessarily all referring to the same example.

Although the operations of the methods herein are shown and described ina particular order, the order of the operations of each method may bealtered so that certain operations may be performed in an inverse orderor so that certain operation may be performed, at least in part,concurrently with other operations. Instructions or sub-operations ofdistinct operations may be performed in an intermittent or alternatingmanner.

The above description of illustrated implementations of the invention,including what is described in the Abstract, is not intended to beexhaustive or to limit the invention to the precise forms disclosed.While specific implementations of, and examples for, the invention aredescribed herein for illustrative purposes, various equivalentmodifications are possible within the scope of the invention, as thoseskilled in the relevant art will recognize. The words “example” or“exemplary” are used herein to mean serving as an example, instance, orillustration. Any aspect or design described herein as “example” or“exemplary” is not necessarily to be construed as preferred oradvantageous over other aspects or designs. Rather, use of the words“example” or “exemplary” is intended to present concepts in a concretefashion. As used in this application, the term “or” is intended to meanan inclusive “or” rather than an exclusive “or”. That is, unlessspecified otherwise, or clear from context, “X includes A or B” isintended to mean any of the natural inclusive permutations. That is, ifX includes A; X includes B; or X includes both A and B, then “X includesA or B” is satisfied under any of the foregoing instances. In addition,the articles “a” and “an” as used in this application and the appendedclaims should generally be construed to mean “one or more” unlessspecified otherwise or clear from context to be directed to a singularform. Furthermore, the terms “first,” “second,” “third,” “fourth,” etc.as used herein are meant as labels to distinguish among differentelements and may not necessarily have an ordinal meaning according totheir numerical designation.

What is claimed is:
 1. A light detection and ranging (LIDAR) systemcomprising: a first optical source to generate a first optical beam; afirst collimating lens to collimate the first optical beam; a firstprism wedge of a first prism wedge pair to redirect the first opticalbeam; a first focusing lens to focus the first optical beam on a frontsurface of a second prism wedge of the first prism wedge pair, thesecond prism wedge to direct the first optical beam toward an outputlens; a second optical source to generate a second optical beam; asecond collimating lens to collimate the second optical beam; a thirdprism wedge of a second prism wedge pair to redirect the second opticalbeam; and a second focusing lens to focus the second optical beam on afront surface of a fourth prism wedge of the second prism wedge pair,the fourth prism wedge to direct the second optical beam toward theoutput lens.
 2. The LIDAR system of claim 1, wherein a spacing of thefirst and second optical beams at the output lens is determined by anangle of the first prism wedge pair and the second prism wedge pair anda first focal length of the first focusing lens and a second focallength of the second focusing lens.
 3. The LIDAR system of claim 1,wherein the first collimating lens is spaced a first distance from thefirst optical source, the first distance corresponding to a focal lengthof the first collimating lens.
 4. The LIDAR system of claim 3, whereinthe second prism wedge is spaced a second distance from the firstfocusing lens, the second distance corresponding to a focal length ofthe first focusing lens.
 5. The LIDAR system of claim 1, wherein theoutput lens creates an angular separation between the first optical beamand the second optical beam.
 6. The LIDAR system of claim 5, wherein theangular separation between the first optical beam and the second opticalbeam is less than two degrees.
 7. The LIDAR system of claim 5, whereinthe angular separation between the first and second optical beams isdetermined by a spacing between the first and second optical beams and afocal length of the output lens.
 8. The LIDAR system of claim 1, whereinthe first prism wedge pair is adjustable to calibrate a first decenterfor the first optical beam with respect to the output lens.
 9. The LIDARsystem of claim 1, wherein the output lens transmits the first opticalbeam to scanner optics of the LIDAR system.
 10. A method, comprising:generating a first optical beam at a first optical source; collimatingthe first optical beam using a first collimating lens; redirecting thefirst optical beam using a first prism wedge of a first prism wedgepair; focusing the first optical beam on a second prism wedge of thefirst prism wedge pair using a first focusing lens; redirecting thefirst optical beam toward an output lens using the second prism wedge;generating a second optical beam at a second optical source; collimatingthe second optical beam using a second collimating lens; redirecting thesecond optical beam using a third prism wedge of a second prism wedgepair; focusing the second optical beam on a fourth prism wedge of thesecond prism wedge pair using a second focusing lens; and redirectingthe second optical beam toward the output lens using the fourth prismwedge.
 11. The method of claim 10, wherein a spacing of the first andsecond optical beams is determined by an angle of the first prism wedgepair and the second prism wedge pair and a first focal length of thefirst focusing lens and second focal length of the second focusing lens.12. The method of claim 10, wherein the first collimating lens is spaceda first distance from the first optical source, the first distancecorresponding to a focal length of the first collimating lens.
 13. Themethod of claim 12, wherein the second prism wedge is spaced a seconddistance from the first focusing lens, the second distance correspondingto a focal length of the first focusing lens.
 14. The method of claim10, further comprising: creating an angular separation of the firstoptical beam and second optical beam using the output lens.
 15. Themethod of claim 14, wherein the angular separation is based on a spacingbetween the first optical beam and the second optical beam at the outputlens.
 16. The method of claim 14, wherein the angular separation betweenthe first optical beam and the second optical beam is less than twodegrees.
 17. The method of claim 10, further comprising: adjusting thefirst prism wedge pair to calibrate a first decenter for the firstoptical beam with respect to the output lens.
 18. The method of claim10, wherein the output lens transmits the first optical beam to scanneroptics.